Reed switch



H. G. MIRBETH REED SWITCH "4 Sheets-Sheet 1 Filed'Feb. 16, 1968 Fm M.

Fm. 1a,

INVENTOR h- 6. M/ZBETH BY u t 0 ATTOZ/VEV Dec. 9, 1969 H. G. MI'RBETH3,48

REED SWITCH Fi 1 1968 4 Sheets-Sheet 3 INVENTOR H 6. M/EBTH UnitedStates Patent US. Cl. 335-205 9 Claims ABSTRACT OF THE DISCLOSURE Apush-button or sliding key embodying a reed contact, adapted to be usedas a feeding key for computing machines, typewriters and the like. Thereed tube and electrical terminals therefor are mounted on thestationary part of the switch, while an annular permanent magnet issupported in encircling relationship about the reed tube in a key slidethat is slidably engaged on the stationary part for longitudinalswitching movement of the magnet relative to the reed tube. The keyslide and stationary parts of the switch are simplified, compact unitarymolded plastic members, and the key knob or push-button body is a hollowshell engageable over the key silde and providing a housing for the reedswitch.

BACKGROUND OF THE INVENTION It is known in connection with sliding orpushing key type switches to employ, instead of open contactarrangements, contacts which are provided inside a sealed capsule calleda reed tube, with the contacts being actuated magnetically from theoutside of the reed tube.

According to a former proposal a construction proved to be good in whicha ball is used inside the reed tube as a freely movable armature whichtouches two adjacent contact elements in each position of the switch,these contact elements consisting of iron rods melted into the tube atthe ends thereof with an air gap therebetween. The non-operative or theoperative position results from the position of the permanent magnetwhich can be moved in the sliding direction and which has the shape ofan annular magnet. Because the permanent magnet is poled in the slidingdirection the ball armature always tends to take a resting position onthe contact elements located next to the permanent magnet. In order toavoid this the ball-type armature is supported in an intermediateposition to one contact element only, so that in practice with a slowmotion of the contacting key both contact elements are notsimultaneously opened or closed. In this type of device the inside drillhole of the annular magnet is made as a slotted hole.

In another former proposal the button knob and key slide form a unit andwhen actuated transmit the pressure into a resiliently supported plasticpart in which the annular magnet is fastened. The stationary reedcontact protrudes through the center opening of the annular magnet sothat the movably arranged part of the armature inside the reed tube iseither closed when the push-button is not pressed (break-contact) oropen when the pushbutton is not pressed (make-contact).

The advantage of these keys is that they require no maintenance andmoreover have a high-life expectancy. However, a disadvantage of suchprior art keys is that they require excessive space due to their length,because the reed contacts must be arranged with their longitudinaldirection parallel to the sliding movement in order to obtain maximumefficiency. Further, the construction of these previously known keysembodying reed contacts are very expensive and are difficult inproduction.

3,483,492 Patented Dec. 9, 1969 ice SUMMARY OF THE INVENTION It isaccordingly a general object of the present inventron to provide animproved push-button or sliding key switch having a reed contact whichis particularly short and compact, being generally similar in size tothe different types of keys having open contacts, and which can bemanufactured generally as simply and economically as said open-contactkeys.

A more particular object of the invention is to provide a push-button orsliding key of the character described embodying a reed contact, whereinthe key knob or push-button body comprises a hollow shell that isengageable over the key slide or movable part of the switch to provide ahousing for the switch.

According to the invention, the reed tube and its electrical terminalsare mounted on the stationary part of the switch, while an annularpermanent magnet is supported in encircling relationship about the reedtube in a key slide that is provided with guide means for slidableengagement of the key slide on the stationary part to move the magnetlongitudinally relative to the reed tube, with the key slide beinginstalled in a body or shell which serves both as the key knob and as ahousing for the switch.

Details of the invention will now be explained With reference to theaccompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1a is a vertical, longitudinalsection, taken on the line 1a1a in FIGURE lb, illustrating the presentinvention on an enlarged scale and showing in particular the manner inwhich the key knob or housing is engaged over and locked to the keyslide.

FIGURE 1b is a side elevational view of the fully assembled switch, asviewed on the line 1b1b in FIG- URE 1a.

FIGURE 2a is a front elevational view of the invention with thepush-button knob removed.

FIGURE 21) is a side elevational view, partly in section, taken on theline 2b2b in FIGURE 2a.

FIGURE 20 is a horizontal section taken on the line 2c2c in FIGURE 2b.

FIGURE 2d is a bottom plan view of the device with the push-button knobremoved, looking in the direction 211-211 in FIGURE 2a.

FIGURE 3a is a horizontal section taken on the line 3zz3a in FIGURE 2a.

FIGURE 3b is a vertical section, partly in elevation, taken on the line3b3b in FIGURE 2a, with the key slide depressed or actuated.

DETAILED DESCRIPTION The key knob 1, which also serves as the housing,is irremovably connected by means of a spring element 2 to the key slide3. To accomplish this, a short portion of the length of spring element 2is fixed in a locking recess 4 in the key slide 3, with the free end ofthe spring element extending into a funnel-shaped recess 5 so as to bemovable therein. When the knob 1 is engaged and fully seated over thekey slide 3, this free end of the spring element 2 is compressed inwedging engagement against the inside wall of the knob to prevent anylongitudinal shifting of the key slide in the recess of said knob.Alternatively, the key slide can be fixed in the key knob in anothermanner it a particularly simple kind of fixing is desired, whilenevertheless retaining a secure frictional engagement between the slideand the knob, even with major stresses. Such alternative fixing involvesthe use of a resilient element consisting of a strip of resilientmaterial, force-lockingly connected with the key slide and supportedagainst the Wall of the recess of the key knob. The resilient elementmay consist of a substantially straight strip of resilient materialwhich is fixed with its center part in a close-fitting recess of the keyslide, and with the free ends of the limbs of the strip projectingbeyond the width of the key slide so that they are supported undercompression against the inside wall of the knob after the knob has beenslid upon the key slide.

The key slide 3 is made of a generally U-shaped spraymolding part asbest illustrated in FIGURE 2c. The side walls of said key slide, i.e.,the U-shaped limbs, are, however, not connected for their entire length,but only at various points by means of transverse straps 6, 7 and 8,whereby the limbs of the U-shaped part can be elastically deformedrelative to each other. Two of these straps, namely the two closelyadjacent ones 7 and 8, fix the permanent magnet in place, whereas thethird connecting strap 6, arranged at a greater distance, bears themeans to fix the key knob on the key slide as described hereinabove indetail.

The permanent magnet is arranged to the rear of the opening 9 in the keyslide between straps 7 and 8, the magnet being an oval-shaped flat ringwhich is poled in the shifting direction and supported between two U-shaped projections or straps 10 and 11 which generally register with theinternal diameter of the annular magnet and are in alignment with theopenings of the magnet. The U-shaped projections or straps 10 and 11 areformed by the respective said straps 7 and 8. These Ushaped projectionsor straps are provided with bearing surfaces 12 which face each other,and at the limb ends projecting edges 13 are provided which serve ashearing and counter-bearing for the permanent magnet. The permanentmagnet is mounted in a very simple way by merely plugging the magnet inbetween the U-shaped projections 10 and 11 in the direction of thelongitudinal axis of the oval, and then turning the magnet around in thegeneral plane of the magnet approximately 90 so that said longitudinalaxis of the oval is generally parallel to the straps 7 and 8, orperpendicular to the plugging direction. This plugging in of the magnetis accomplished with a so-called snap-in effect, because the side wallsof the key slide are resilient.

A reed contact 14 protrudes into the center opening of the permanentmagnet in such a way that the armature parts, movably arranged withinthe reed tube, are either closed or opened. The reed tube may consist ofglass into which two contact elements 15 are melted at one end and twoother contact elements 16 are melted at the other end. A freely movablearmature, having the shape of a ball, may be provided between the endsof said contact elements inside th glass tube, thereby bridging,depending on the position of the annular magnet relative to the reedtube, either both contact elements 15 or both contact elements 16. Theposition of the annular magnet results from the position of the keyslide, since the annular magnet is shifted with the key slide. The freeends of the contact elements are fixed outside of the reed tube on thestationary part 17 of the switch, and are there electrically connectedwith the external terminals which may have the shape of pins or wires 18and 19 for the respective contact elements 15 and 16.

The stationary part 17 of the switch is a substantially plate-shapedspray-molding provided on its inside with a forwardly facing groove 20extending along the sliding direction, into which groove a helicalresetting spring 21 is inserted. The longitudinal groove 20 issemi-cylindrical in cross-section, corresponding to the shape of thehelical spring 21. In the switch-off condition, shown in FIG- URE 2a,the helical spring touches the stopping surfaces of the longitudinalgroove at both ends of the spring. One of these stopping surfaces isformed by a cylindrical stop member 22, fitting the diameter of thegroove, which is inserted into the groove at its lower end. The upperstopping surface of the longitudinal groove is provided by projections23 on the stationary part which protrude into the groove, but whichleave sufficient space for a shoulder member 24 on the key slide to moveinto the groove when the switch is actuated. In the switch-on positionthe helical spring is thus supported at its lower end by the cylindricalstop member 22 and at its upper end by the shoulder member 24 on the keyslide under a certain compression thereby producing the resilient orspring force required to restore the key slide to its switchotfposition.

As a guide for the sliding movement between the key slide and stationarypart, the key slide is provided on its free limb ends with guidingsurfaces fitting the shape of the stationary switch part 17. Oneguiding'surface has the shape of a semi-cylindrical groove fitting thediameter of the helical spring 21 used as a restoring spring. Thisguiding surface is arranged relative to the semicylindrical-shapedgroove 20 in the stationary switch part 17 in a mirror-like arrangementso that the helical spring 21 and the cylindrical stop member 22 slideon this surface when the key is actuated. Another guide surface isformed by the web or strap portion of the key slide which terminates atthe shoulder member 24. Further guiding surfaces, which are best seen inFIGURES 2c and 3a are forwardly facing surfaces 25 and 26 near therearward of free ends of the respective sides of the key slide andrearwardly facing surfaces 27 and 28 on the respective sides of the keyslide offset forwardly from the respective surfaces 25 and 26. Theguiding surfaces 25, 26, 27 and 28 are all oriented generally at rightangles relative to the direction of the sides of the key slide. All ofthe aforesaid guide surfaces in the key slide, as well as the otherelements of construction of the key slide, are arranged relative to eachother in such a way that the key slide can be spray-molded without usingmold slides.

The reed contact 14 is supported on the stationary part 17 of the switchby means of substantially square, spaced projections 29 and 30 at theupper and lower ends of the spray molding, these projections 29 and 30protruding forwardly a sufficient distance to locate the reed tube inthe axis of the annular permanent magnet. A pair of drillholes 31 extendthrough the projection 29 parallel to the side walls of the key slideand have the external terminal pins or wires 18 inserted therein inclosely fitting relationship, while a similar pair of drillholes 32extend through the projection 30 parallel to the side walls of the keyslide and have the external terminal pins or wires 19 inserted thereinin closely fitting relationship. End portions of the terminal pins orwires 18 extend forwardly from the respective drillholes 31 and are benttoward each other so as to fit loosely into transverse grooves 33 withtheir free ends located in a centralaperture 35 and electricallyconnected with the respective contacting elements 15 at the lower end ofthe reed tube, as by soldering. Similarly, the external terminal pins orwires 19 have end portions which extend forwardly of their respectivedrillholes 32 and are bent toward each other so as to fit loosely intotransverse grooves 34, with their free ends disposed in a centralaperture 36 and electrically connected with the respctive contactingelements 16 at the upper end of the reed tube, as by soldering. Theupper surface of the projection 29 adjacent the lower end of the reedtube and the lower surface of the projection 30 adjacent the upper endof the reed tube are arranged as respective oblique surfaces 37 and 38so that the contact elements do not touch the insulating material of thestationary part, which might impair the soldering pro cess and damagethe connections. For the same reason the bent ends of the terminal pinsproject somewhat from their respective guiding grooves as shown inFIGURE 2b.

The grooves 34 are defined between lower and upper projections 39 and40, respectively, arranged in a mirrorlike relationship. Spaced,protruding edges 41 and 42 are formed on the key slide by the U-shapedprojection or strap 11, and these protruding edges 41 and 42 are engagedunder the projections 39 in a snap-in effect when the key slide ismounted on the stationary part 17 of the switch. The mounting of the keyslide, with the annular magnet already inserted therein, on thestationary part 17, in which the helical spring has already beeninserted, is accomplished by a simple plugging of the key slide onto thestationary part with a simultaneous application of a small pressing andshifting force. Thereupon a stop pin 43 is inserted into a hole 44formed in the upper projection 30 of the stationary switch part 17. Thisstop pin 43 cooperates with an oppositely located, upwardly facing stopshoulder 45 in the key slide to determine the uppermost limit of slidingmovement of the key slide on the stationary switch part. The reedcontact 14 is then affixed to the key by soldering the contact elements15 and 16 to the associated terminal pins 18 and 19, respectively. Arectangular aperture 46 is provided in the key slide between the straps6 and 7 to give access for soldering the contact elements 16 to theterminal pins 19, while soldering of the contact elements 15 to theterminal pins 18 can be easily accomplished from the outside.

The oustide terminal pins or wires 18 and 19 may be led out in thedirection of their respective drillhole axes as indicated in phantomlines in FIGURES 2b, 2c and 2d and inserted into a printed circuitboard, being electrically connected to the conductors of the printedcircuit board by dip-soldering. In this case the key would be installedwith the longitudinal or shifting axis of the key parallel to thesupporting or circuit board, and for installation of the key in thisposition a plurality of fixing tenons 47 project rearwardly from theplate-shaped spray molding which forms the stationary switch part 17.These tenons 47 are fitted into corresponding openings in a supportingor circuit board composed of insulating material and are riveted to suchboard by deformation of the tenons under heat.

If the key is to be mounted with its axis or sliding directionperpendicular to the board, the external terminal ends or wires are bentapproximately parallel to the axis of the key or the shifting directionand led to the outside at the bottom surface of the stationary switchpart, at the opposite end thereof from the knob. The bent parts of pinsor Wires 19 are secured in position by being inserted betweenlongitudinally extending projections or ribs 48 and 49 which extendalong the rear surface of the plate-shaped molding part 17. Integrallyformed on the lower end of the plate-shaped molding is a generallyrectangularly shaped bottom plate 50 which has a pair of spaced slots 51therein for receiving the respective terminals 18 and a pair of somewhatlonger spaced slots 52 therein for receiving the respective terminals19. The external terminal pins are inserted into these slots 51 and 52in such a way that they project downwardly from the bottom plate 50 inthe axial or sliding direction and are arranged in patterned spacing. Itis thereby possible to insert the projecting ends of the terminal pins18 and 19 into respective openings in a circuit board also arranged in apattern and to connect the terminal ends with the printed conductorlanes by dip-soldering. It is advantageous to have the terminals 19 notonly spaced laterally from the terminals 18, but also in the frontreardirection, so as to increase the spacing between the terminals andprovide electrically safe connections between the terminals and theprinted circuit conductors which will not adversely influence eachother.

In order to affix the stationary part 17 of the switch in this uprightposition on a circuit board, the bottom plate 50 thereof is providedwith downwardly projecting tenons 53 and 54 which can be inserted intosuitable openings of the board and riveted to the board.

It will be seen from the foregoing detailed description that the slidingor pushing key with a reed contact according to the present inventionhas a number of advantages compared to former known constructions. Thus,the key is very compact and requires only a small number of components.Aside from the knob or housing, a total of only six components are usedfor the key, namely, the key slide, the stationary part, the pressurespring, the reed contact, the annular magnet and Wire for the externalsoldering connections and the stopping pin. These parts can bemanufactured simply and reliably. The key slide and stationary parts ofthe switch are so shaped that they can be spray-molded without moldingslides or pitches. This results in low production costs quite comparableto the production costs for keys with open contacts. Assembly of theindividual components is also simple, so that the costs therefor arevery low. The annular magnet is afiixed solely by inserting it into anundercut in the key slide and turning it through an angle ofapproximately 90. When mounting the pressure spring the conventionalthreading thereof is not required. The key slide and stationary switchpart are connected simply by plugging under a light pressure andshifting. The knob or housing is mounted in a most simple way by meansof a self-locking resilient element. Plastic pins are used to installthe key, permitting a number of different possibilities for attachmentof the key. The key can be inserted into printed circuits as well asplaced on a U-rail or installed into sets of keys. Moreover, it ispossible to install the key in different directions, either in theshifting direction or perpendicular to it. The dimensions of the keycorrectly fit existing key sets. The keys according to the presentinvention are further suitable for computing machines and typewriterswherein the keys are used as feed-in keys. Another application may, forexample, be as feed-in keys for cargo elevators.

While the instant invention has been shown and described herein in whatare conceived to be the most practical and preferred embodiments, it isrecognized that departures made be made therefrom within the scope ofthe invention, which is therefore not to be limited to the detailsdisclosed herein, but is to be accorded the full scope of the claims soas to embrace any and all equivalent devices.

What is claimed is:

1. A reed switch which comprises a stationary switch part having a reedtube supported thereon, a key slide slidably mounted on said stationarypart for movement between unactuated and actuated positions, said keyslide having a permanent magnet supported therein adjacent said reedtube for operating the contacts of the reed tube, spring means engagedbetween said stationary part and key slide biasing said key slidetowards its said unactuated position, and a key knob in the form of ahollow shell engaged over said key slide and serving as a housing forthe switch, said key slide being a generally U-shaped molded plasticpart having a transverse forward web portion and a pair of free limbportions extending rearwardly from opposite sides of said forward webportion, first guide surface means on said limb portions of said keyslide and second guide surface means on said stationary part, said firstand second guide surface means being complementary and defining thedirection of sliding movement of the key slide on the stationary part.

2. A reed switch as defined in claim 1, wherein said spring means is ahelical spring, and said first and second guide surface means includerespective opposed, generally semicylindrical surfaces defining agenerally cylindrical cavity within which said helical spring isdisposed.

3. A reed switch as defined in claim 1, wherein said permanent magnethas the general shape of a flat ring oriented with the general planethereof substantially perpendicular to the sliding direction, said ringbeing in encircling relationship around the reed tube.

4. A reed switch as defined in claim 3, wherein said stationary switchpart is a generally plate-shaped molded part having said second guidesurface means formed on the sides thereof, said stationary partincluding a pair of forwardly projecting studs spaced apart in thesliding direction, the reed tube being supported adjacent its ends onthe respective said studs with the reed tube spaced forwardly of thebody of the stationary part intermediate said studs sufficiently toprovide clearance for the rearward portion of the magnet ring engagedaround the reed tube. A

5. A reed switch as defined in claim 4, wherein the reed tube hascontact means at both ends thereof, said studs each having forwardlyopening paseage means therethrough, and terminal pin means electricallyconnected to said contact means at each end of the reed tube andextending through said passage means of the respective stud andprojecting externally of the switch.

6. A reed switch as defined in claim 3, wherein said key slide includesa pair of generally U-shaped straps extending transversely between saidlimbs of the key slide adjacent to said forward web portion of thelatter, said straps being spaced apart in the sliding direction andsupporting said ring-shaped magnet therebetween, and opposed shouldermeans projecting into the space between said opposed bearing surfacesgenerally at opposite sides of the key slide peripherally engaging themagnet so as to secure the magnet in place between said generally U-shaped straps.

7. A reed switch as defined in claim 6, wherein the periphery of saidgenerally ring-shaped magnet is oval, thereby adapting the magnet to besnap-fitted between said opposed shoulder means by insertionbetween'said generally U-shaped straps and said opposed shoulder meansgenerally in the direction of the longitudinal axis of the oval withsuch axis generally parallel to the limbs of the key slide and thenrotating the ring approximately 90 to snap the end portions of the ovalinto interlocking abutment against said opposed shoulder means.

8. A reed switch as defined in claim 6, wherein said forward web portionof the key slide is formed by a plurality of transverse straps spaced inthe sliding dir ction connecting said limbs, said straps beingelastically deformable to permit relative flexing between said limbs,and two of said straps comprising said U-shaped straps.

9. A reed switch which comprises a stationary switch part having a reedtube supported thereon, a key slide slidably mounted on said stationarypart for movement between unactuated and actuated positions, said keyslide having a permanent magnet supported therein adjacent said reedtube for operating the contacts of the reed tube, spring means engagedbetween said stationary part and key slide biasing said key slidetowards its said unactuated position, and a key kno'b in the form ofa'hollow 'shell engaged over said key slide and serving as a housing forthe switch, said switch including a resilient element supported on saidkey slide and resiliently engageable against the inside of said key knobshell, said resilient element permitting slidable engagement-of the keyknob into assembled position over the key slide but resisting removal ofthe key knob from the key slide so as to retain the key knob in its saidassembled position.

References Cited UNITED STATES PATENTS 3,271,530 9/1966 Wirsching.3,283,274 11/1966 De Falco 335-206 BERNARD A. GILHEANY, Primary ExaminerR. N. ENVALL, JR., Assistant Examiner US. Cl. X.R.

